Would like to mount the Holosun on my M&P 9. Pros or Cons? If pro, what mounting platform do I use?

Unless I’m reading the specs wrong, that is a very large sight, more suited for a carbine than a pistol. It appears to need a rail. Maybe you could give more details on what you are thinking, or better specs that would work on a pistol.

The gold standard is a Trij RMR milled into your slide with co-witnessed elevated iron sights.

I have one mounted on the top pic rail of an Extar EP9 (AR9 platform pistol), and it's fantastic. However, it would be way too big for a regular pistol.

I am not very well versed on these accessories. I will do more research. I want to avoid milling my slide and the high cost of the Trijicon.

Thanks for your advice

Then may I suggest you try to find one or more different setups with owners who will let you shoot with them. There are many ways to approach this from cheap and almost worthless to expensive and so very helpful for speed and accuracy, especially for older eyes, that it can be worth the expense.

You will get what you pay for, but you are correct that you need to know what you want first.

with more and more pistols being milled fore the CORE style slide cut, SOMEONE will likely bring a @$200 option soon.

I'll JUMP on a long slide M&P if they ever make a 10mm. But if they don't come soon, a RIA 1911A2 HC 10mm is looking likely.

Hi.. joined just to reply to this thread, haha. The handgun version of the 510C you're after is the Holosun 507C which uses the RMR mounting pattern. Holosun specifically made this because so many Glock owners have RMR cuts but don't want to spend $400+ on an optic. These run $299 but I'll bet they hit $249 during Black Friday.

However, if you're in the market for one, I'd add it to your notify lists on sites that carry it because they sell out within a couple hours of being updated due to how popular they are. Holosun can't keep up with the market demand on them lol. I've currently got one backordered at Primary Arms for my high-end custom Glock 19 build. Can't wait to finally get it.

Good first post Bewsii. 507c certainly looks like it’s trying to directly compete with the King Trij RMRs but at a better price. They have a way to go to prove durability, quality and adequate supply.

I am confused by reports and photos showing the mounting system for this optic.
Is there an optional saddle that fits on top of the slide?
Only for a Glock profile?
Is it removable so the actual unit can be put much lower in a milled notch without the lower saddle mount?
And the sight looks rather tall for cowitness sights?

Yes, it can be used with or without the supplied mount. I suspect that's included in case you wanted to run it on something like a small rifle that uses picatinny rails.

Without the mount, it's designed to mount directly inside milled RMR cuts. I don't know if you can use adapter plates like those suppled with Glock MOS systems to mount it on non-RMR slides. The Holosun 510C is quite popular with the AR15 crowd due to it's success in competing with the Eotech's for half the price. Alabama Shooter on youtube is known for his rugged testing of optics, and he shot one with a shotgun, reinstalled on his AR and it kept functioning perfectly lol. That pretty much blew the market open for Holosun. I have a 510C on my 7" AR9 build and it's very nice for the $215 I paid for it.